1. Field of the Invention
The present invention concerns the structure of an amplifier and, notably, that of a microwave amplifier. It constitutes an improvement designed to increase the electrical efficiency of the amplifier.
It is becoming indispensable to increase the electrical efficiency of field-effect transistors for present as well as future electronic systems, because of the increase in the number of circuits. To obtain this improvement in performance characteristics, it is necessary to:
improve the technology for making the transistors;
reduce the losses of the passive matching circuits.
The invention concerns the latter point.
2. Description of the Prior Art
It is known that the characteristics of a transistor biased below its pinch-off voltage are not reproducible. They depend on the technology used to make the component, and no manufacturer guarantees these characteristics.
But it is also known that if a voltage, far greater in terms of absolute value, is applied to the gate of a field-effect transistor, this transistor is subjected to a sort of hysteresis: when the gate voltage returns to a value between the pinch-off voltage and the maximum gate voltage, the transistor does not respond immediately. It stays off for a certain time, during which the input signal is not amplified. This corresponds therefore to a diminishing of efficiency and to an unnecessary dissipation of energy.